The use of point to multi-point systems, where various modems send information to each other using the same physical medium, is known in the prior art. The main problem in these systems is that unless the transmission network is symmetrical for each user, something that is unlikely to occur in reality, the user modems receivers will not be able to receive information from the various transmitters at equal levels of quality due to the fact that attenuation and channel noise in the downstream (the channel that runs from a user modem transmitter to the receiver in another user modem) depends on which transmitter and receiver are involved in each case and the behaviour of the channel at each moment.
This problem makes it very difficult to maintain both the bandwidth requirements and the maximum latency necessary to be able to transmit different types of traffic in the point to multi-point systems available to date.
Furthermore, in cases where the transmission medium response in time is variable rather than fixed, as is the case of low voltage electricity networks or mobile networks, this technical problem becomes more important due to the need to modify the configuration of the communication so as to be able to maintain the requirements for latency and bandwidth at all times.
The current invention solves this technical problem, allowing said quality of service requirements (bandwidth and maximum latency) to be maintained independently of the characteristics of the physical medium and the communication.
Other systems that allow the inclusion of quality of service (QoS) in a communication exist in the prior art. In this context mention must be made of the Spanish Patent submission No 200003024 concerning a “POINT TO MULTIPOINT SYSTEM AND PROCESS FOR THE TRANSMISSION OVER THE ELECTRICITY NETWORK OF DIGITAL DATA”, as well as Spanish Patent submission No 200100916 concerning a “PROCESS FOR MULTIPLE ACCESS AND MULTIPLE TRANSMISSION OF DATA IN A MULTI-USER SYSTEM FOR THE POINT TO MULTIPOINT DIGITAL TRANSMISSION OF DATA OVER THE ELECTRICITY NETWORK”, both of which present a solution for the inclusion of quality of service (QoS) for communication point to multi-point over the electricity network, and where a single transmitter (the head-end modem) communicates with various users (user modems). The process in the present invention improves this process to allow the inclusion of quality of service (in terms of bandwidth and maximum latency) in point to multi-point communications, so that any user modem may transmit information to any other user and the communication is not limited to a variable time medium such as the low voltage electricity network but can also be employed in any other transmission medium used as a communications channel in point to multi-point transmissions.
Another relevant background art can be found in document EP 0 973 290 A2 which relates to multiplexing data packets in a data service channel with data in one or more digital video signals channels to form a multiplexed output signal. The data in the data service channel may include control data, conditional access data, electronic program guides, paged data services, service information, broadcast internet information, and business information such as financial share information. The data packets each comprise a time stamp indicating a requested delivery time and the data packets are sorted into a queue in time stamp order. The urgency of the data service channel is calculated as a function of the queue length and requested delivery times. The share of the bit rate of the multiplexed output signal allocated to the data service channel is varied according to its urgency. An error value is calculated for each data packet to represent the error between the expected delivery time and the requested delivery time to the head of the queue and the urgency of the data channel is derived as an average of the error values. The average may be a weighted average.
Therefore, the present invention presents a process that maintains said requirements including when attenuation, noise and channel response vary dynamically not only in frequency but also in time for each user modem.